Pumps are staple engineering components used in a variety of applications to transfer fluid. They are available in a wide range of sizes and capacities to suit particular applications. One typical application is that of supplying lubricating oil in an automotive engine. Vane pumps are used widely in engine oil and transmission oil pumping applications. Vane pumps comprise vanes slidably engaged with a rotor. The vanes move radially in the rotor while also sliding along the inner surface of an eccentric cavity in a pump casing.
In engine oil applications the reliable operation of the pump is paramount to avoid catastrophic failure of the engine. On the other hand a reduction in both the cost, weight and energy requirements of the pump is demanded to meet automotive manufacturer's objectives.
Conventionally, pumps have a rotor supported within a housing on a pair of bearings. The bearings are located on opposite walls of the housing and the rotor has an integral shaft supported in those bearings. The shaft is usually press fit into the rotor which can cause significant stress to be imposed on the rotor. This arrangement may require an exotic material to withstand the stresses caused by the press fit while ensuring torque transmission at cold temperatures. It also requires careful alignment of the bearings that are located in independent housings of the pump to permit the shaft to be rotated freely within the bearings. Any misalignment in the bearings can cause the rotor to be tilted within the housing, causing premature wear and/or increased or decreased clearance with a consequent loss of efficiency or mechanical drag. Similarly, misalignment of the bearings imposes side loads upon the shaft which inhibits rotation and increases the torque required to drive the pump and thereby an increase in fuel consumption when used in an automotive environment. As such the conventional pumps do not readily meet the increasingly stringent requirements for enhanced efficiency and lower costs.
Representative of the art is U.S. Pat. No. 5,964,584 discloses a vane pump for liquids is comprised of a slotted rotor supported in a stator, wherein radially displaceable vanes are slidingly disposed, which can be pressed slidingly supported while acted upon by centrifugal force, spring tension or otherwise by compressive force against a stator inside wall, in said process delivery cells are formed which expand or narrow in a crescent-like fashion and the entry of the liquid takes place through a hollow concentric stator and the filling of the vane cells from the inside to the outside. The rotor is shaftless and of tubular construction, both sides are extended beyond the operating area determined by the vanes and the rotor is supported with the extensions in the outer stator, while the rotor possesses continuous vane slots from the internal to the external diameter. In the area of the rotor extensions, the frame of the stator possesses on its surface hydraulic effective surfaces acted upon by the operating pressure and/or pressure-relieved directed against the rotor for the at least partial compensation or avoidance of radially occurring forces.
What is needed is a vane pump having a rotor having a position that is axially controlled between case cavity walls and a shaft engaged with the rotor. The present invention meets this need.